This invention relates to deposition of a phenolic compound on a dyed textile fiber to prevent color loss, especially by chemical attack from solutions of chlorine bleach, and to improve colorfastness.
Polymeric coatings have been applied to textile fibers to solve a wide range of problems. It is well known that melamine-formaldehyde, urea-formaldehyde, thiourea-formaldehyde and phenol-formaldehyde resins may be applied to cellulosic fibers to impart anti-creasing properties, prevent shrinking and for fixation of dyestuffs. Additionally, these resins have been found to protect dyed cellulose textiles from color loss when they are exposed to chlorine solutions. In Landolt, U.S. Pat. No. 2,373,191, a process is disclosed for combining a dyed fiber, such as cotton, which has been treated with one of the aforementioned resins and cured, with a fiber, such as wool, which is to be treated in a chlorine solution to prevent shrinkage. Subsequent application of a chlorine solution to the fiber mixture should not discolor the dyed cotton fiber. Recently, formaldehyde has been targeted as a hazardous chemical in the work place and its use has become severely restricted. Other drawbacks of the urea-formaldehyde type resins include yellowing and stiffness imparted to the treated fiber.
A number of known processes are directed to providing permanent press or anti-shrink properties to wool and blends of wool fibers with some type of polymeric film. For example, Intermacom A.G.'s British Patent 1,259,082 discloses in situ formation of a polyamide film on a textile fiber. In situ film formation may be achieved by interfacial polymerization using a diamine and diacid chloride or diacid ester. Alternatively, a polyamide emulsion or solution may be applied to a textile fiber and cured, such as in Coe, U.S. Pat. No. 2,890,097. These processes have limited applications to the treatment of carpet, since they tend to impart a harsh hand to the finished product and have not been demonstrated to impart bleach resistance to dyed textile fibers.
Textile floor coverings, particularly polyamide pile carpet, have been the focus of a variety of protective treatments. Sulfonated phenol-formaldehyde condensation products, styrenemaleic anhydride copolymer and polymers and copolymers of methacrylic acid have been applied to polyamide fibers to prevent staining, and represent the "stain blocker" technology. Ozone protection has been sought by coating polyamide fibers with one or more of N,N'-disubstituted thioureas, polythioureas, tertiary amines formed by the reaction of epoxides and amines and organic phosphites. Also, a combination of film-forming polyvinyl chloride and water insoluble organic phosphate ester has been applied to polyamide fiber to provide flame retardancy.
Despite the availability of the aforementioned treatments, serious shortcomings remain in protecting floor covering from discoloration by bleach. This problem is especially prevalent at health care installations where bleach solutions are routinely used to disinfect furniture, equipment, fixtures, and the interior of the building. Even a spill of a dilute bleach solution, as low as 0.05 wt. % solution of sodium hypochlorite, can ruin a section of carpet.
One approach to eliminating the risk of discoloration caused by bleach has been to provide solution dyed fibers. Thus, the dye is incorporated into the polymer melt prior to spinning. The colorant is evenly distributed throughout the cross-section of the fiber. If the fiber is later exposed to bleach, only the dye at the surface will be affected and the overall color of the fiber will not be significantly diminished.
Nevertheless, solution dyed fibers have several drawbacks, not the least of which is that they are more expensive to produce. Further, solution dyed fibers introduce additional complications to the manufacturing process. Large inventories of each color of fiber must be maintained rather than a single inventory of undyed fibers, which can later be dyed to the desired color. If patterning is desired, one must either tuft the carpet with two or more different colored yarns or print the pattern over the base color. The first alternative is very expensive. Overprinted patterns, which are only applied to the surface of the fiber, are typically used, but the patterns are subject to bleach attack.
In addition to the problems encountered from bleach attack, many dyed textile fibers, especially those incorporated into floor coverings, are susceptible to wet crocking. The problem is frequently encountered during shampooing, where the combination of mechanical agitation and detergents particularly is severe.